Filigree swagings may be produced by means of laser beams. FIG. 1 shows a known device for this process. 1 denotes a laser light source, 2 denotes a switch (optical or electric), 3 denotes a focus control, 4 denotes a beam guide, 5 denotes a workpiece, 6 denotes a swaging, 7 denotes a control device, 8 denotes a sensor (depth sensor, location-sensing), 9 denotes a workpiece table, 10 denotes a laser beam, and 11 denotes the z axis adjustment of the worktable. The plane of projection is considered as the x-z plane, as schematically shown. The y axis is perpendicular to the plane of projection.
A laser beam 10 is generated in the laser 1. 2 symbolizes an ON/OFF tracer which may be designed as a q-switch, as well as an intensity control device. Traced and, if necessary, level controlled laser light then reaches the focus control 3 which is able to adjust the focal position in the z direction. After that, the laser light passes through a beam guide 4 which may consist e.g. of mirrors positioned at right angles to each other. The mirrors are capable of rotating within specified angle ranges and thus can effect that the point of impingement of the laser beam 10 on the workpiece 6 is controlled in the x-y plane.
The material is ablated by liquefaction and vaporization, respectively, of the material on the surface of the workpiece. For this purpose, the focus of the laser beam is positioned on the surface of the workpiece so that there will be a high area performance input such that the material melts and vaporizes and is thus removed. The laser beam is guided area-wise over the exposed surface in accordance with swaging data for the swaging to be produced. 6 indicates the already produced (partial) swaging, 6a symbolizes the outer surface of the desired finished swaging. The ablation is carried out in layers. When one layer has been ablated, the workpiece table 9 is lifted together with the workpiece 5 by a height corresponding to one layer so that the next layer may now be ablated.
The focus adjustment device 3 is used to compensate the non-planar spherical cap, which as a rule is ball-shaped and on which the focus of the laser beam moves in case of a deflection in the x and y directions. This will be explained in more detail with reference to FIG. 3.
The control device 7 controls the individual components (laser 1, switch and intensity control device 2, focus adjustment device 3, beam guide 4, z axis 11). It obtains the data to be introduced by referring to swaging data 12, which may e.g. be CAD data, and to other parameters as well, if necessary.
FIG. 2 shows the focus adjustment device 3 in more detail. Coming from the laser 1 and the switch 2, respectively, the laser beam 10 at first passes through a diverging lens 21 and then one or more converging lenses 22, 23. The diverging lens 21 can be repositioned in the z direction by an adjustment device 24. Different courses of ray result therefrom and lead to the fact that corresponding to a repositioning of the diverging lens 21 the focal position will in the end also be repositioned in the z direction. Two courses of ray are schematically indicated, i.e. one by solid lines and another by dashed lines. The positions of the lenses are denoted by P1 and P2, respectively. Along with the different positions P1 and P2, different focal positions f1 and f2 are generated. They are denoted by 20-1 and 20-2 and differ from each other by Δz. The possible maximum of Δz is referred to as a stroke.
FIG. 3 shows a usual method for the production of a swaging and the usual application of the focus adjustment device. In FIG. 3 and generally in this description same components are denoted by the same reference numerals. 6 symbolizes the swaging already finished in part. 31a, b and c symbolize the layers to be ablated one after the other. In the embodiment as shown the laser beam 10 is guided over the area in the direction of the arrow 30 along a specified path. The material melts and evaporates, respectively, at the point of impingement and is thus removed. 32 denotes the outer surface of the swaging part to be produced in the following. 33 denotes the surface which has already been exposed. As the laser is guided in the x and y directions by means of rotatable mirrors, its focal point 20 does not move on a plane in space but on a generally ball-shaped, arched spherical cap 34. This could easily lead to the laser beam and its focus 20 being within the layer to be ablated at best only in some parts thereof when it is guided over the area. In other areas an intrafocal or an extrafocal portion of the laser beam would impinge on the surface of the material, with the result that the energy density would not be sufficiently high, the material would not evaporate or only to a minor degree and consequently the ablation performance would decrease or become very uneven.
In order to compensate for this effect, the focus adjustment device is used in known ablation methods and ablation devices, respectively. In the end, it corrects the focal position difference between the easily adjusting spherical cap 34 and the desired position in the plane as symbolized by the straight line 35. Thus, the focus adjustment device changes the focal position in the z direction depending on the respective momentary x and y position of the laser beam in order to adjust the focus to the plane 35 in correspondence to the momentarily ablated layer 31a. 
When a layer has been completely ablated the z axis mechanically follows by the height of one layer. In FIG. 1 this may e.g. be carried out by lifting the workpiece table 9 by means of a position member 11. Through this adjustment the next layer (31b) is ablated similarly. The disadvantage of this method is that the mechanical guiding of the swaging in the z direction is time-consuming. This shows particularly in the case of small swagings wherein the adjustment time in the z direction is comparatively long in comparison to the machining time for ablating a layer.
FIG. 3 shows another disadvantage of the known ablation in layers: 32 symbolizes the desired (theoretical) outer surface of the swaging to be produced last. However, due to the ablation in layers, the result is in fact a nonideal but real course, as shown at 33: Due to the ablation in layers the wall proceeds in steps, with the height of the steps corresponding to the thickness of the layer. Depending on the desired quality of the outer surface of the swaging this may be perceived as a bigger or smaller disadvantage.
It is the object of the invention to provide a method and a device for the formation of a swaging which allow the fast production of small swagings as well and the formation of smooth outer surfaces of swagings.
This object is achieved by means of the features of the independent claims. Dependent claims are directed to preferred embodiments of the invention.